OG bug: Lara's shadow briefly disappear after pulling block

[aredfan]

Cf: #870

[rr-]

I see two ways out of this – we can either remove the Room_AlterFloorHeight in favor of bridge-like floor functions, or delay the call to Room_AlterHeight until Lara's animation finishes. The first solution, while in general more elegant, will drive us into more corner cases when it comes to enemy pathfinding and sideways collision (as floor/ceiling only work in the Y axis).